Dead Birds Reported, Tested, and Positive
for WNV by County in California in 2025
Year To Date (Weeks 1 - 14)

(2025-04-03) - Source: http://westnile.ca.gov

CountyReported*TestedPositive% Tested Positive
Alameda12311100%
Alpine----
Amador1---
Butte15---
Calaveras4---
Colusa5---
Contra Costa142---
Del Norte----
El Dorado16---
Fresno31---
Glenn6---
Humboldt4---
Imperial1---
Inyo----
Kern13---
Kings5---
Lake83--
Lassen----
Los Angeles163---
Madera5---
Marin17---
Mariposa----
Mendocino2---
Merced15---
Modoc----
Mono1---
Monterey9---
Napa7---
Nevada10---
Orange709--
Placer55---
Plumas----
Riverside445--
Sacramento200---
San Benito3---
San Bernardino29---
San Diego9334--
San Francisco25---
San Joaquin33---
San Luis Obispo16---
San Mateo15651--
Santa Barbara175--
Santa Clara171---
Santa Cruz24---
Shasta6---
Sierra----
Siskiyou2---
Solano45---
Sonoma43---
Stanislaus28---
Sutter3---
Tehama4---
Trinity----
Tulare9---
Tuolumne3---
Ventura46---
Yolo81---
Yuba2---
State Totals181110811%

* Birds in a die-off are not included in reported totals because the deaths are not related to WNV. A die-off is defined as a group of 10 or more same species dead birds unless the species is American Crow.
Source: Vector-Borne Disease Section, California Department of Public Health